1. Field of the Invention
The present invention relates to gate valves and more particularly relates to gate valves of the type designed for operation with high temperature, high pressure fluids such as those generated in coal gasification processes and the like. Specifically, the present invention is an improvement of the type of gate valve disclosed in a copending application of Henry A. Waller, Ser. No. 082,969, filed concurrently herewith and assigned to the same assignee as the present invention.
2. Description of the Prior Art
Over the years, a wide variety of gate valves and slide valves of various types have been developed. U.S. Pat. No. 380,037 discloses a valve for steam engines wherein valve members are supported on curved bows and are pressurized to expand against the opposing valve seats. U.S. Pat. No. 1,783,329 discloses a gate valve wherein opposite valve members are biased outwardly against the seats by a pair of coil springs. U.S. Pat. No. 2,541,968 discloses a gate valve wherein sloped wedging surfaces are provided for moving a pair of valve members outwardly against facing annular valve seats. U.S. Pat. No. 2,778,600 discloses a gate valve wherein leaf springs are provided for biasing a pair of valve gates to slide in a longitudinal direction with respect to each other and wedging forces are provided to cause the valve gate to move laterally apart for seating. U.S. Pat. No. 2,826,391 discloses a wedge valve wherein valve elements are wedged outwardly apart against valve seats. Another wedge valve is shown in U.S. Pat. No. 2,861,770. U.S. Pat. No. 3,478,771 discloses a sectional body gate valve with a valve seat scraper device having springs biasing the valve members apart from one another. U.S. Pat. No. 3,815,868 discloses a double disc gate valve wherein rotatable valve discs are used and are wedged apart for seating. Said copending Waller application discloses a double disc gate valve wherein the valve discs are supported by a pair of flexure elements which normally bias the valve discs away from the confronting valve seats when the valve gate assembly is in a valve seat confronting position. The discs are interconnected by an upwardly bowed flexure element which is retained between upper and lower holding members connected to the transversely extending valve stem of the gate valve. A downward force is exerted on said bowed flexure element to flatten it and force the valve discs outwardly into engagement with the opposed valve seats.